Stent, method for processing stent, and method of stenting a patient

ABSTRACT

The subject invention relates to a stent with respect to which the occurrence of artifacts in nuclear spin tomography can be reduced or avoided. The subject invention also pertains to the etching of stents, incorporating titanium and/or titanium alloys, that have been processed with tools containing magnetizing components. The subject invention can also be useful for the control of in-stent-restenosis by allowing imaging under nuclear spin tomography to see in-stent-restenosis in the interior of the subject stent.

CROSS-REFERENCE TO RELATED APPLICATION

[0001] This application is a divisional of U.S. patent application Ser. No. 10/091,988, filed Mar. 5, 2002, which claims the benefit of German Application Serial No. 20104145.6, filed Mar. 9, 2001.

BACKGROUND OF INVENTION

[0002] The subject invention relates to a stent which exhibits a low incidence of artifacts in nuclear spin tomography, and to a process for treating stents that are processed with tools containing magnetizing components such as iron.

[0003] In today's stent technology it is desirable to use cardiovascular stents that are able to adequately prop open the vessel and that can be accurately positioned. It would be desirable to use stents that can be viewed with nuclear spin tomography. However, traditional stents are made of stainless steel and show distinct image distortions, or so called artifacts. These artifacts occur when materials with high magnetic susceptibility are used.

BRIEF SUMMARY OF THE INVENTION

[0004] The subject invention relates to a stent with respect to which the occurrence of artifacts in nuclear spin tomography can be reduced or avoided. The subject invention also pertains to the etching of stents, incorporating titanium and/or titanium alloys, that have been processed with tools containing magnetizing components. As processing the stents with tools containing magnetizing components can result in some amount of the tool material rubbing off the tools onto the stent, etching the stent in an etch solution that etches the magnetizing component materials of the tools can reduce the amount of the magnetizing component materials of the tools on the surface of the stent and, therefore, reduce the incidence of artifacts from the stent.

[0005] The subject invention can also be useful for the control of in-stent-restenosis by allowing imaging under nuclear spin tomography to see in-stent-restenosis in the interior of the subject stent.

DETAILED DESCRIPTION OF THE INVENTION

[0006] In a specific embodiment, the subject stent can incorporate an alloy of 3 percent aluminum by weight and 2.5 percent vanadium by weight, with the remainder being titanium, known as material TIAl3V2.5 or material No. 3.7194 or 253.7195 (ASTM Grade 9), where ASTM is the American Society for Testing and Materials. As known in the art, the composition of titanium alloy TIAl3V2.5, also known as Ti3Al2.5V and ASTM Grade 9, is shown in Table I. TABLE I Content (weight %) C  up to 0.08% N₂  up to 0.03% O₂  up to 0.15% V 2.0-3.0% Al 2.5-3.5% Fe  up to 0.25% H₂ up to 0.015% Ti balance

[0007] The use of TIAl3V2.5 to produce this embodiment of the subject stent results in a stent that produces especially few image artifacts and has sufficient hardness to be suitable for interventional instruments used in nuclear spin tomography.

[0008] In another specific embodiment, the subject stent can incorporate an alloy referred to as ASTM Grade 5 (also known as ISO 3.765 or 3.7165). The alloy according to ASTM Grade 9 is harder than an alloy according to ASTM Grade 5, which can have the following components: 90% titanium, 6% aluminum, and 4% vanadium. As known in the art, the composition of titanium alloy known as ASTM 5 is shown in Table II. TABLE II Content (weight %) C  up to 0.08% N₂  up to 0.05% O₂  up to 0.2% V  3.5-4.5% Al 5.5-6.75% Fe  up to 0.4% H₂ up to 0.015% Ti balance

[0009] The ASTM Grade 5 material is more flexible than the ASTM grade 9 material and is, therefore, more suitable for expanding a stent with the help of a balloon catheter.

[0010] Stents, incorporating materials that are made to be artifact free, that are created with tools containing magnetizing components typically show an increase in screen artifacts. This increase in artifacts is due to some amount of the tool material rubbing off the tool onto the stent during the processing of the stent with the tools. A reduction of surface magnetism of the stent can be achieved through dipping in etching solutions that etch the materials the tools are made of. The rub-off from the tools is eliminated by the wet chemical etching solution. In a specific embodiment, such an etching solution, that removes iron impurities can consist of, for example, 3 parts hydrochloric acid and 2 parts saltpeter acid. This etching solution can be further reduced with additional parts water in the etching process.

[0011] Stents manufactured in accordance with the subject invention, in the manner described herein, can be ideally observed in nuclear spin tomography units incorporating a magnetic flux density>1.0 Testa. In a specific embodiment, unexpanded stent having a diameter of 1 mm was balloon expanded to a diameter of 4 mm, and it was possible to clearly see all the stent struts, or the so-called strats. It was also possible to get a good look inside the expanded stent. Advantageously, so-called in-stent-restenosis in the interior, or inner lumen, of the stent can be seen when a stent has been treated in accordance with the subject invention. The ability to see in-stent-restenosis in the interior of the stent can be useful for the control of in-stent-restenosis. 

1-5. (canceled).
 6. A stent, comprising: TIAl3V2.5, wherein the TIAl3V2.5 exhibits a low incidence of artifacts in nuclear spin tomography.
 7. The stent according to claim 1, wherein the stent consists essentially entirely of TIAl3V2.5.
 8. The stent according to claim 1, wherein the stent is viewable in nuclear spin tomography.
 9. The stent according to claim 1, wherein TIAl3V2.5 has the following composition by weight: up to 0.08% C; up to 0.03% N₂; up to 0.15% O₂; 2.0% to 3.0% V; 2.5% to 3.5% Al; up to 0.25% Fe; less than 0.015% H₂; and the balance Ti.
 10. The stent according to claim 2, wherein TIAl3V2.5 has the following composition by weight: up to 0.08% C; up to 0.03% N₂; up to 0.15% O₂; 2.0% to 3.0% V; 2.5% to 3.5% Al; up to 0.25% Fe; up to 0.015% H₂; and the balance Ti.
 11. A stent, comprising: TIAl6V4, wherein the TIAl6V4 exhibits a low incidence of artifacts in nuclear spin tomography.
 12. The stent according to claim 6, wherein the stent is expandable with a balloon catheter.
 13. The stent accrediting to claim 6, wherein the stent consists essentially entirety of TIAl6V4.
 14. The stent according to claim 6, wherein the TIAl6V4 has the following composition by weight: up to 0.08% C; up to 0.05% N₂; up to 0.2% O₂; 3.5% to 4.5% V; 5.5% to 6.75% Al; up to 0.4% Fe; up to 0.015% H₂; and the balance Ti.
 15. The stent according to claim 8, wherein the TIAl6V4 has the following up to 0.08% C; up to 0.05% N₂; up to 0.2% O₂; 3.5% to 4.5% V; 5.5% to 6.75% Al; up to 0.4% Fe; up to 0.015% H₂; and the balance Ti. 